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1

Clinical Electromyography (EMG)

used to evaluate the scope of neuromuscular disease or trauma as well as assist with establishing anticipated goals and expected outcomes

2

Forms of clinical EMG:

Nerve conduction velocity (NCV)
Electromyography (needle EMG)

3

Kinesiological EMG

used to study muscle activity and establish the role of various muscles in specific activities
Electromyography (primarily surface EMG)

4

Biofeedback

describes the use of instrumentation to make covert physiological processes more apparent to the patient

5

Best and most widely used electrodes:

silver silver chloride

6

How many electrodes:

2 active
1 isolation

7

What do the 2 active electrodes do?

primarily sense the activity of the muscle

8

What does the isolation electrode do?

make sure the two active electrodes only pickup electricity that is coming from the patient

9

Where are the active electrodes placed?

both active electrodes are generally placed at the midpoint of the muscle being recorded in line with the muscle fibers

10

Considerations for placing electrodes:

Place electrodes in position of movement
Consider how skin may shift over the underlying muscle during movement

11

What does closer spacing of the electrodes give?

smaller sampling are and lower amplitude of signals

12

What does wider spacing of the electrodes give?

larger sampling area and higher amplitude of signals

13

What is volume conduction?

the salt water conducts electricity through its volume and allows us to record from the surface of the skin

14

What is cross talk?

when the electrodes are far apart you can get recordings from other muscles

15

What is an artifact?

an excess or erroneous signal that is detected and displayed but does not come from the electrical activity of motor neurons or muscle tissue

16

What are the different types of artifact?

movement
power line interference
EMG

17

Movement artifact:

shift on the screen that is from the movement of wires not electrical activity

18

Power line interference:

if the reference ground isn’t on the pt and eliminating electrical interference

19

What happens during the processing phase?

filtering
rectification and integration
time constant
amplification
goal/threshold

20

What is filtering:

generally, the electrical signal from the pt is filtered to only allow frequency components of 80-250 Hz to pass

21

What is rectification and integration:

so that it makes more sense for us to look at and appreciate change

22

Time constant:

we can determine how fast the display on the screen follows changes in electrical activity of muscle

23

Low time constant (low smoothing)

screen displays changes very quickly to follow changes in muscle activity (see moment to moment changes)

24

High time constant (high smoothing)

Screen display does not change quickly to follow changes in muscle activity (seeing overall effect)
Screen does not change with every step

25

Amplification (gain/sensitivity)

Can be used to adjust the size of an EMG signal on a given display

26

Goal/threshold:

some level of EMG that a pt can be prompted to contract up to or relax down to, gives the pt something to shoot for

27

Display Phase

display mode
audio feedback to patient

28

Types of display mode

continuous
work/rest

29

Continuous:

the unit continuously displays the pts electrical activity along with any goals or other feedback

30

Work/rest:

The unit prompts the pt to contract toward the goal for a specific period of time and then prompts the pt to relax for a specific period of time
Turns on the display when you are likely to contract and turns it off when you’re likely to be resting